Package Archive And Canonical Metadata

cabin package and cabin publish --dry-run run the same staging pipeline:

Validate the package's cabin.toml.
Walk the source tree under a fixed include / exclude policy.
Build a deterministic .tar.gz archive whose root holds cabin.toml.
Compute the archive's SHA-256 digest.
Generate canonical per-version JSON metadata in the same shape a Cabin file registry serves to consumers.
Write both files into --output-dir (default dist/).

cabin publish --dry-run adds a "no registry was modified" report. The dry-run path is local-only: nothing is uploaded, no registry mutation happens, and cabin publish without --dry-run exits with a clear error unless a local --registry-dir is provided.

Source archive format

Archives are gzipped tar files conforming to the extractor contract:

the archive root contains a file named cabin.toml;
only regular files and directories are emitted; symlinks, hard links, char/block devices, fifos, and other tar entry types are rejected with a clear error;
all entry paths are relative; a path containing .., an absolute path, or one that would escape the package root is rejected.

The default <output-dir>/<name>-<version>.tar.gz filename is conventional; the in-archive path layout is what registries and extractors care about.

Determinism

The same logical input always produces byte-identical archives:

the file enumeration is sorted lexicographically by relative path;
each tar header has mtime, uid, gid zeroed and username and groupname cleared so the archive does not embed who built it;
mode is 0o644 for regular files; directories are implied by the extractor and are not emitted as explicit entries;
the gzip header carries mtime = 0 and OS code 0xff (unknown) so the archive bytes do not depend on when or where the build ran.

cabin package re-running with identical input succeeds silently because the on-disk artifact already matches what the current run would produce. If the on-disk archive or metadata file has different bytes the run fails with output file already exists with different bytes; remove the file and re-run.

Include / exclude policy

By default the archive includes every regular file under the package root and excludes a small fixed list of generated / dependency / VCS artifacts:

Excluded	Reason
`.git/`, `.hg/`, `.svn/`	VCS state.
`.cabin/`	Package-local Cabin caches plus the typed `.cabin/config.toml` file (config patches and `[source-replacement]` declarations live here). Local config is user policy, not package source spec, so it never enters published archives. See `config.md` and `patch-overrides.md`.
`build/`	Default `cabin build` output directory.
`dist/`	Default `cabin package` output directory.
`node_modules/`	Convention for JavaScript-style dependencies.
`.DS_Store`	macOS Finder metadata.
`compile_commands.json`	Generated tooling index.
`build.ninja`	Generated Ninja build file.
`cabin.lock`	Generated lockfile.

Directory names are matched anywhere in the tree, not only at the root, so nested submodules / build trees do not leak in.

A .cabinignore file format is not part of the current local archive format and should not be implemented opportunistically.

Package validation

Before archive bytes are written, cabin-package validates:

the manifest parses (existing cabin-manifest rules);
the manifest contains a [package] table — workspace-only roots are rejected with cannot package workspace root without a [package] section; pass --manifest-path for a package;
the package name is path-safe for registry publishing: names containing /, \, .., leading dots, control characters, or Windows drive prefixes are rejected with package name "<name>" is not path-safe for registry publishing;
no declared dependency uses path = "...". Path dependencies are not publishable and produce cannot package path dependencyfoo; path dependencies are not publishable;
no declared dependency uses { workspace = true } without workspace context. The CLI passes a workspace-resolved Package from cabin-workspace::load_workspace when packaging a workspace member, so the inherited requirement is substituted before metadata generation. A standalone cabin package --manifest-path <member>/cabin.toml (no workspace context) errors with dependency 'foo' uses workspace = true, but package metadata was generated without workspace resolution;
target source paths and include directories stay inside the package root (lexically — .. walking is rejected).
the manifest does not declare a [patch] table. Patches are local development policy; cabin package returns package "<name>" declares a [patch] table; patches are local development policy and not publishable. Remove the [patch] table from this manifest before packaging, or move the patches to a .cabin/config.toml file. See patch-overrides.md.

Symlink / hard-link / unsupported file-type errors are raised later, during archive enumeration:

refusing to package symlinkbecause symlinks are not supported
refusing to packagebecause only regular files and directories are supported

If the archive enumeration yields no cabin.toml at the root the run fails with package archive would not contain cabin.toml.

Canonical metadata

{
  "schema": 1,
  "name": "fmt",
  "version": "10.2.1",
  "dependencies": {
    "zlib": ">=1.2.0, <2.0.0"
  },
  "dev-dependencies": {
    "gtest": "^1.14"
  },
  "system-dependencies": {
    "openssl": { "version": ">=3" }
  },
  "features": {
    "default": ["simd"],
    "features": { "simd": [], "ssl": [] }
  },
  "yanked": false,
  "checksum": "sha256:<archive-sha256>",
  "source": {
    "type": "archive",
    "path": "../artifacts/fmt/fmt-10.2.1.tar.gz",
    "format": "tar.gz"
  }
}

Field	Description
`schema`	Always `1`.
`name`, `version`	From `[package].name` and `[package].version`.
`dependencies`	Normal-kind versioned registry dependencies (`[dependencies]`). Path / workspace dependencies cause validation to fail before metadata is generated.
`dev-dependencies` (optional)	`[dev-dependencies]` versioned dependencies. Omitted when empty.
`system-dependencies` (optional)	Entries declared with `system = true` in any of the dependency tables, grouped by package name: `{ name -> { "version", "dependency_kind" } }`. Omitted when empty. Every declared system dependency is required; the metadata document has no `required` field. Cabin never resolves or fetches these — they round-trip purely as metadata, and `cabin build` probes them via `pkg-config`.
`target` (optional, per-entry)	Canonical inner-expression form of a `cfg(...)` predicate copied from `[target.'cfg(...)'.<kind>]`. Present on Cabin package and system dep entries declared under a target table; absent otherwise. The wrapping `cfg(...)` is implicit. See `target-dependencies.md`.
`features` (optional)	The package's `[features]` declarations. Omitted from the JSON when no features are declared.
`toolchain` (optional)	The workspace root's `[toolchain]` plus any `[target.'cfg(...)'.toolchain]` overrides, exactly as written in the manifest. Environment- or CLI-derived selections are deliberately not written here. Omitted when no `[toolchain]` table was declared. See `toolchains.md`.
`build` (optional)	The package's `[profile]` plus any `[target.'cfg(...)'.profile]` overrides. Omitted when empty.
`compiler_wrapper` (optional)	The workspace root's `[profile.cache]` plus any `[target.'cfg(...)'.profile.cache]` overrides, written as the typed compiler-wrapper declaration model. Environment- or CLI-derived wrapper selections are deliberately not written here. Omitted when no cache table was declared. See `compiler-cache.md`.
`yanked`	Always `false` from `cabin package`.
`checksum`	`sha256:<hex>` digest of the archive bytes the run produced.
`source.type`	Always `"archive"`.
`source.format`	Always `"tar.gz"`.
`source.path`	File-registry relative reference: `../artifacts/<name>/<name>-<version>.tar.gz`. Dry-run staging does not publish that path, but the value matches the package-index `source` block shape used by file-registry publish.

The metadata document is rendered with serde_json::to_string_pretty in struct-declaration order, dependencies sorted by name, and a trailing newline. Repeated runs over the same input produce the same bytes.

CLI surface

cabin package \
  [--manifest-path <path>] \
  [--output-dir <path>] \
  [--format human|json]

Default --manifest-path is cabin.toml, default --output-dir is dist, default --format is human.

cabin publish --dry-run \
  [--manifest-path <path>] \
  [--output-dir <path>] \
  [--format human|json]

Same defaults. cabin publish without --dry-run and without --registry-dir exits with actual publishing requires --registry-dir, or use --dry-run.

Output layout

dist/
  <name>-<version>.tar.gz
  <name>-<version>.json

Re-running with identical input is idempotent: if the on-disk file already matches the current run's bytes, the file is left alone and the run succeeds. If the bytes differ, the run fails with output file already exists with different bytes; the user is expected to remove the file and re-run.

File-Registry Publish

File-registry publish runs on top of the same staging pipeline. cabin publish --registry-dir <path> calls cabin-package's stage() to produce the same archive bytes + canonical metadata, then hands them to cabin-registry-file to write into a local file registry. The registry layout is described in registry-design.md; the on-disk shape of each per-package file is the same one this document defines.

Behavioral notes specific to registry publish:

source.path in the registry's packages/<name>.json is the registry-relative "../artifacts/<name>/<name>-<version>.tar.gz", regardless of what the dry-run dist/<name>-<version>.json happened to carry. The registry crate normalizes this so static sparse-HTTP serving can read the same layout without rewriting.
Duplicate (name, version) publishes fail with a clear error.
Existing artifact bytes are never silently overwritten; if an artifact file is present without a matching index entry, the publish run refuses.

Scope

cabin-package and cabin-publish are the local-only archive and file-registry surface. The repository-wide scope policy in docs/architecture.md tracks broader registry direction.